Re: [HACKERS] [PATCH] Generic type subscripting - Mailing list pgsql-hackers

From Dmitry Dolgov
Subject Re: [HACKERS] [PATCH] Generic type subscripting
Date
Msg-id 20210119142514.nkevvvf7a2ux4553@localhost
Whole thread Raw
In response to Re: [HACKERS] [PATCH] Generic type subscripting  ("Dian M Fay" <dian.m.fay@gmail.com>)
Responses Re: [HACKERS] [PATCH] Generic type subscripting  (Pavel Stehule <pavel.stehule@gmail.com>)
List pgsql-hackers
> On Thu, Jan 14, 2021 at 12:02:42PM -0500, Dian M Fay wrote:
> > Other than that, since I've already posted the patch for returning an
> > error option, it seems that the only thing left is to decide with which
> > version to go.
>
> The trigger issue (which I did verify) makes the "no update" option
> unworkable imo, JavaScript's behavior notwithstanding. But it should be
> called out very clearly in the documentation, since it does depart from
> what people more familiar with that behavior may expect. Here's a quick
> draft, based on your v44 patch:
>
> <para>
>  <type>jsonb</type> data type supports array-style subscripting expressions
>  to extract or update particular elements. It's possible to use multiple
>  subscripting expressions to extract nested values. In this case, a chain of
>  subscripting expressions follows the same rules as the
>  <literal>path</literal> argument in <literal>jsonb_set</literal> function,
>  e.g. in case of arrays it is a 0-based operation or that negative integers
>  that appear in <literal>path</literal> count from the end of JSON arrays.
>  The result of subscripting expressions is always of the jsonb data type.
> </para>
> <para>
>  <command>UPDATE</command> statements may use subscripting in the
>  <literal>SET</literal> clause to modify <type>jsonb</type> values. Every
>  affected value must conform to the path defined by the subscript(s). If the
>  path cannot be followed to its end for any individual value (e.g.
>  <literal>val['a']['b']['c']</literal> where <literal>val['a']</literal> or
>  <literal>val['b']</literal> is null, a string, or a number), an error is
>  raised even if other values do conform.
> </para>
> <para>
>  An example of subscripting syntax:

Yes, makes sense. I've incorporated your suggestion into the last patch,
thanks.

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